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From: Michal Hocko <mhocko@kernel.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	stable@vger.kernel.org
Subject: Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM
Date: Thu, 23 Aug 2018 21:25:47 +0200	[thread overview]
Message-ID: <20180823192547.GS29735@dhcp22.suse.cz> (raw)
In-Reply-To: <20180823154648.GD12066@tassilo.jf.intel.com>

On Thu 23-08-18 08:46:48, Andi Kleen wrote:
> On Thu, Aug 23, 2018 at 04:28:12PM +0200, Vlastimil Babka wrote:
> > Two users have reported [1] that they have an "extremely unlikely" system
> > with more than MAX_PA/2 memory and L1TF mitigation is not effective. Let's
> > make the warning more helpful by suggesting the proper mem=X kernel boot param,
> > a rough calculation of how much RAM can be lost (not precise if there's holes
> > between MAX_PA/2 and max_pfn in the e820 map) and a link to the L1TF document
> > to help decide if the mitigation is worth the unusable RAM.
> 
> I'm not sure anyone would really do that. After all you probably prefer
> your memory. And if it's really a non ECC client part they are are
> already used to to live very dangerously because their undetected RAM bit error
> rate will be significant. L1TF is probably one of your smaller problems
> in this case...

There are people who care about L1TF mitigations. I am not going to
question their motivation. In any case a hint how to make the mitigation
active again sounds more useful than something that sounds as scary as
"you are vulnerable".

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-08-23 19:25 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-23 13:44 [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has too much RAM Vlastimil Babka
2018-08-23 13:56 ` Michal Hocko
2018-08-23 14:28 ` [PATCH] x86/speculation/l1tf: suggest what to do on systems with " Vlastimil Babka
2018-08-23 15:46   ` Andi Kleen
2018-08-23 19:25     ` Michal Hocko [this message]
2018-08-23 19:38       ` Andi Kleen
2018-08-23 20:05         ` Michal Hocko
2018-08-23 22:07           ` Andi Kleen
2018-08-23 19:03   ` kbuild test robot
2018-08-23 19:23   ` kbuild test robot
2018-08-23 19:27   ` Michal Hocko
2018-08-24  7:32     ` Vlastimil Babka
2018-08-24  7:55       ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka
2018-08-24 10:36       ` [PATCH] x86/speculation/l1tf: suggest " Vlastimil Babka
2018-08-24 12:10         ` Vlastimil Babka
2018-08-24 12:20           ` Michal Hocko
2018-08-24 13:57       ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka
2018-08-23 15:44 ` [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has " Andi Kleen
2018-08-23 20:20   ` Vlastimil Babka
2018-08-24  2:22   ` Andre Tomt
2018-08-24  3:35     ` Andi Kleen
2018-08-29  2:04     ` Christopher Snowhill
2018-08-24  8:52   ` xxxxxx xxxxxx
2018-08-24  7:55 ` [tip:x86/urgent] x86/speculation/l1tf: Fix " tip-bot for Vlastimil Babka

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